Telematics units within mobile vehicles provide subscribers with connectivity to a telematics service provider (TSP). The TSP provides subscribers with an array of services ranging from emergency call handling and stolen vehicle recovery to diagnostics monitoring, global navigation system aided position identification, map services, and turn-by-turn navigation assistance. Telematics units are often provisioned and activated at a point of sale when a subscriber purchases a telematics-equipped vehicle. Upon activation, the telematics unit can be utilized to provide a subscriber with telematics services such as those described herein.
One telematics service provided by TSPs is a Global Navigation Satellite System (GNSS) based navigation service. GNSS is a generic term referring to any of multiple satellite constellation-based global positioning networks including, for example, the Global Positioning System (GPS) constellation. Another GNSS constellation network is the Global Navigation Satellite System (GLONASS). A particular example of a GNSS based navigation service is one providing turn-by-turn (TBT) directions to a telematics unit based upon a specified destination and current conditions including the current location of the telematics unit. Several other GNSS systems are currently under development and are capable of providing at least partial positioning functionality.
Navigation-related services may be provided to vehicles using a combination of GNSS-based navigation services in combination with a dead reckoning (DR) measurement system. DR measurement involves calculating a current position based on a previously known position using known speed and heading information since the previously known position was determined.
The above body of information is provided for the convenience of the reader. The foregoing describes a suitable environment for which the described system and method are provided, and is not an attempt to review or catalog the prior art.